Devices of this type are known from the document FR-A-2.212.521, in which the vibrating trough forms a trough containing a bath of liquefied gas, and FR-A-2.674.320, in which the products are placed in contact with a thin film of liquefied gas useful for most applications. In the known devices, the wall of the bottom of the vibrating trough is constituted by a smooth metallic sheet ,which is supposed to promote the spreading of the liquid film and the sliding without hindrance of the products. The applicant has nevertheless found, that for products that do not have a very irregular external shape, and in particular for such products of transverse dimensions greater than 3 cm or substantially flat products, the extended contact between a substantially flat surface of the product and the smooth metal sheet at the bottom of the channel does not permit good circulation of the liquefied gas below the product and hence gives rise to noticeable gradients of freezing in this latter.